The invention relates, in particular, to a method for reducing the energy consumption of a motor vehicle having at least one vehicle electric system, to which at least a first electric consumer (also known as a load) is connected.
The number of electric consumers in motor vehicles has increased dramatically. In order to reduce the emission of CO2 in the vehicle, hydraulically operating consumers are being replaced by electric consumers. Thus, for example, one option is to replace the hydraulic steering of the motor vehicle with an electric power steering (EPS). However, such electric consumers can, in a short period of time, overtax the vehicle electric system with their high power demand. The result is that there is also a high demand that the electric system of the motor vehicle be stable. In particular, when high loads occur for a short period of time, adequately high electric voltage or rather electric power must be available.
There is therefore needed a method that makes it possible to achieve an efficient vehicle electric system and, in addition, to reduce the energy consumption of a motor vehicle.
This and other needs are met by a method and/or vehicle electric system for reducing the energy consumption of a motor vehicle having at least a first electric consumer coupled to the vehicle electric system. In a first operating mode of the motor vehicle, the level of the electric load on the vehicle electric system, without at least the first consumer, is at a first higher level. In a second operating mode of the motor vehicle, the level of the electric load on the vehicle electric system without at least the first consumer is temporarily decreased to a second level that is lower than the first level. A device, which is intended for detecting the driving situation and is provided in the vehicle, recognizes an imminent specific driving situation on the basis of the previous behavior of the driver in controlling the vehicle and/or behavior of the vehicle in advance, and initiates a temporary switch in the level of the electric load on the vehicle electric system to the second lower level. Advantageous embodiments of the invention are described herein.
One aspect of the invention consists of the fact that in a first operating mode of the motor vehicle, the level of the electric load on the vehicle electric system, without at least the first consumer, is at a first higher level. For example, both the electric generator of the vehicle and the battery of the vehicle feed jointly the vehicle electric system in order to supply the higher electric load or rather the electric consumers (or loads) with adequate electric voltage. In this situation, for example, the generator can be loaded largely to full capacity.
In a second operating mode, the level of the electric load on the vehicle electric system without at least the first consumer is temporarily decreased to a second level that is lower than the first level in a second operating mode of the motor vehicle. As a result, the first consumer (or rather its induced load) on the vehicle electric system is excluded.
A device, which is intended for detecting the driving situation and is provided in the vehicle, recognizes an imminent specific driving situation on the basis of the previous behavior of the driver in controlling the vehicle and/or the behavior of the vehicle in advance and initiates a temporary switch in the level of the electric load on the vehicle electric system to the second lower level.
In this second operating mode, the vehicle electric system supplies, in particular, the “power hungry” consumers that are currently really necessary for normal driving with an adequately high electric voltage and/or electric power. Then, these consumers react in the expected, especially comfortable manner. If, for example, during a cornering maneuver or rather during a cornering action the electric steering system is activated during the first higher load level, the result may be a significant collapse in the voltage in the vehicle electric system owing to the additional load on the vehicle electric system. This situation, in turn, causes the electric steering to become stiff—a state that both makes the driver uncertain, especially during a cornering maneuver, which is usually supposed to be carried out quickly, resulting in a sharp drop in comfort and convenience.
The term “temporary” is defined preferably as calculating the period of time in such a way that the driver can safely cope with the imminent driving situation with simultaneous involvement of the respective electric consumers without any loss in comfort and convenience.
One embodiment of the invention provides that in order to achieve the second lower level of the electric load on the vehicle electric system, the power consumption of at least one electric heating device of the motor vehicle is reduced or the at least one electric heating device of the motor vehicle is turned off. In this case, it concerns preferably a seat heater, a rear windshield heater, a washing jet heater, a mirror heater, a steering wheel heater, and/or a front windshield heater. Heating devices are generally quite sluggish, so that their short term cutoff or power reduction will hardly be perceived by the driver as having an adverse effect.
One embodiment of the invention provides that in order to achieve the second lower level of the electric load on the vehicle electric system, the power consumption of at least one electric comfort consumer is reduced or the at least one electric comfort consumer is turned off. In this context especially “inconspicuous” comfort consumers in the event of a short term cutoff or power reduction are the so-called heating devices.
One embodiment of the invention provides that the device for detecting the driving situation takes into consideration who the current driver is and what his previous behavior was. The current driver can be recognized, in particular, with the aid of the vehicle key that he uses. In this way, the hit rate for predicting that a cornering action is imminent can be raised. If, for example, the device for detecting the driving situation recognizes that the driver in question always swerves during a cornering action (a maneuver that is not always done by every driver), this criterion can be weighted higher in the algorithm for recognizing a cornering action.
One embodiment of the invention provides that the electric consumer is an electrically operated steering system of the motor vehicle, and the imminent specific driving situation is a cornering action. This is a driving situation in which a low electric voltage in the vehicle electric system can be perceived by the driver as especially unpleasant.
One embodiment of the invention provides that the position of the accelerator pedal (also referred to herein as a driving or gas pedal) is detected by the device for detecting the driving situation, and the level of the electric load on the vehicle electric system is switched to the second lower level, when the pedal is largely in its rest position, and at least one additional driving situation occurs. Even this feature is a characteristic of an imminent cornering action and furnishes an important indicator of an imminent cornering action.
A further development of the invention provides that the acceleration and the speed of the vehicle are detected by the device for detecting the driving situation, and the level of the electric load on the vehicle electric system is switched to the second lower level, when the acceleration of the vehicle is negative, the speed falls below a predetermined threshold value, and at least one additional driving situation occurs. This state, too, is characteristic of an imminent cornering action and furnishes an important indicator of an imminent cornering action.
In an additional embodiment of the invention the steering angle of the electric steering system of the vehicle is detected by the device for detecting the driving situation. The level of the electric load on the vehicle electric system is switched to the second lower level, when the absolute value of the steering angle is greater than a predetermined threshold value, and at least one additional driving situation occurs. This state may be an indicator that the driver is beginning to make a swerving maneuver or rather a cornering maneuver. Since many drivers swerve before a cornering action, such a swerving action may be an additional useful criterion, in order to recognize at an adequately early time an imminent cornering action.
An additional embodiment of the invention provides that the steering angle of the electric steering system of the vehicle is detected by the device for detecting the driving situation, and the level of the electric load on the vehicle electric system is switched to the second lower level, when the absolute value of the steering angle is greater than a predetermined speed-dependent steering threshold or rather steering angle threshold, and at least one additional driving situation occurs. If the driver does not swerve prior to a cornering action, this characteristic of an imminent cornering action may replace the “swerving criterion” and may raise the reliability of the prediction of an imminent cornering action.
A preferred embodiment of the invention provides that the device for detecting the driving situation checks whether the vehicle is making a swerving maneuver. Swerving can furnish a very clear sign of an imminent cornering action.
A further development of the invention provides that the device for detecting the driving situation checks whether the brake pressure is higher than a predetermined brake pressure or rather a tolerance pressure and, in addition, checks whether the speed is less than a predetermined acceleration-dependent speed value and/or a dynamic cornering threshold. In this way the reliability of the prediction of a cornering action can be increased even more.
In addition, the invention proposes a vehicle electric system of a motor vehicle that exhibits a program-controlled device, which is intended for detecting the driving situation and carries out the method of the invention. Furthermore, the invention proposes a program-controlled device, which is intended for detecting the driving situation and which carries out the method of the invention or initiates its execution.
The inventive method is described in detail below with reference to the flow charts using a cornering action as an example. Identical reference numerals and symbols show the same functions or functions that have the same effect.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.